Syringes are used by medical personnel to withdraw blood from patients, inject intravenous medications into patients, inject intramuscular medications into patients, prepare irrigation solutions, prepare dialysis fluids, prepare intravenous pushes, prepare bolus fluids, prepare intravenous fluids for parenteral injection, and prepare oral dose medications. Personnel trained to prepare solutions, pushes, or other fluids for injection prepare the solutions within a laminar flow hood or a vertical flow hood using aseptic technique. The hood provides a work area, which reduces the probability of contaminants being introduced into the intravenous admixtures or other solutions during their preparation, by providing clean, filtered air over the work area. Vertical flow hoods and biohazard hoods additionally reduce the probability of escape of biohazard materials being used from the work area and hood. Theses hoods are commonly found in hospital settings and used for both manufacture and incorporation of additives into parenteral and ophthalmic products. The intravenous fluids, admixtures, and other solutions are prepared by placing a bag or bottle of fluid for injection, along with a needle, syringe, and the injectable medication, into the delineated work area in the hood. The medication is drawn from an ampoule, ampul, ampule, or vial, for example, into the syringe using a needle and is then injected into the bag of intravenous fluid for injection. The fluid for injection can be a push bag, minibag, large volume parenteral, lipids or fat emulsion, etc. The bag or bottle of fluid for injection, apart from its therapeutic value, functions as a vehicle for delivering the medication, electrolytes, or other additives to the patient intravenously.
The individuals preparing the intravenous solutions are typically gowned, gloved, and use aseptic technique during the course of preparing the intravenous fluids. When preparing solutions for injection, it is necessary for the individual preparing the intravenous fluids to move their hands in and out of the laminar flow work area and also out of the laminar flow hood. Accordingly, while the hands are outside the work area and the hood, contaminants in the outside environment are introduced onto the hands or gloves of the individual preparing the intravenous solutions. In addition, the outer packaging used to hold the intravenous additives, ampoules, vials, syringes, needles, and other items used in preparing the solutions is not sterile and can carry contaminants which can be transferred or deposited onto the hands and fingers or gloves of the individual preparing the intravenous admixtures. While aseptic technique is used by the personnel preparing the solutions to reduce the tendency of introducing contaminants into the solutions being prepared, these contaminants can gain entry into the medication that has been drawn-up into the syringe barrel by their being deposited onto the inside surfaces of the syringe barrel by way of the barrel opening and/or plunger. Accordingly, care must be exercised to prevent the entry of dust, lint, dirt, hair, glass fragments, etc., and other contaminants into the syringe barrel. Although not encouraged, inadvertent contact of the plunger shaft—touch contamination—typically occurs with the hands, fingers, or gloves during the preparation of a solution. If the air, hands, fingers, hair, clothing, gloves, etc., are carrying contaminants such as dirt, lint, viruses, bacteria, microorganisms, dust, germs, pathogens, pyrogens, glass fragments, paper fibers, cloth fibers, foreign particles, hair, etc., then these contaminants can be deposited onto the plunger shaft surface and/or fall into the rearward barrel opening and subsequently be deposited onto the inner barrel walls. While a handle portion is usually located on the rearward end portion of the plunger to aid an individual in sliding the plunger into and out of the syringe barrel, larger syringes are typically difficult to handle using only one hand, or even both hands, because of the syringe size, plunger length, and friction created by surface area contact between the internal wall surfaces of the syringe barrel and the plunger piston surface. As a result, the plunger is often grasped by its shaft to gain leverage, for aiding the individual preparing the intravenous fluids, in pulling the plunger and piston along the hollow or cavity of the inner syringe barrel length to draw medication into the syringe cavity. Because the barrel end is open, grasping the plunger shaft allows contaminants present on the hands, fingers, hair, clothing, gloves, etc., to be deposited on the plunger shaft. These contaminants may also fall into the rearward end opening of the syringe barrel and come in contact with and deposit on the inner surfaces of the syringe barrel. The outside surfaces of the piston and the medication in contact with the inside syringe barrel surfaces can pick up these contaminants and ultimately deliver them to the solutions being prepared. Infusion of a pathogen or other contaminates into a patient has the potential to cause infection in the patient. Infusing or injecting solutions containing contaminate particulate matter into a patient has the potential of introducing thrombi and vessel blockage. Syringes and plungers currently in use do little to discourage the introduction of contaminants onto the plunger shaft and inner syringe barrel surface. The current syringes also suffer from problems of piston failure or detachment of the piston from the forward end of the plunger shaft causing loss of the seal between the piston and the inner surfaces of the syringe barrel. When this occurs, medication in the syringe barrel leaks or flows out of the syringe barrel rearward end opening and onto the hands, fingers, gloves, and work surface. When the material is blood or the medication or additive being used to prepare the solutions is a biohazard material such as certain chemotherapy drugs, acids, or radioactive pharmaceuticals or radiopharmaceuticals, the safety of the individual working with the material is compromised because of exposure to and contact with the hazardous material.
On occasion, nurses or other personnel are required to prepare intravenous admixtures because of a patient's immediate requirement for a medication. These admixtures are prepared in non-sterile environments and generally without the use of aseptic technique. Occasionally, it is necessary for syringes containing medication or other materials to be left at bedside in a patient's room or attached to intravenous or other types of tubing for intermittent dosing. During this time, the plunger shaft and rearward opening of the syringe barrel remain exposed to the environment increasing the probability of medication contamination. The syringes of the instant invention provide an added level of protection to the medication and patient when working in a non-sterile environment.
An additional problem which plagues current syringe designs is the problem resulting from pulling the forward end of the plunger and piston to close to the rearward end opening of the syringe barrel cavity leading to accidental separation of the plunger and piston from the barrel. Also, when the piston and forward end of the plunger are withdrawn along the syringe barrel cavity and positioned close to the rearward syringe barrel opening, the plunger shaft and medication in the syringe cavity is in increased jeopardy of contamination. Additionally, any rocking motion caused to the plunger shaft while in this position tends to compromise the seal between the piston and the syringe barrel inner surface causing leaking of the medication from the syringe barrel. The instant invention overcomes the drawbacks noted above.